1. Field of the Invention
The present invention relates to a composition for manufacturing a polyester resin, and more particularly, to a composition for manufacturing a polyester resin having excellent transparency, excellent color, and high inherent viscosity (I.V) suitable for molding containers.
2. Description of the Related Art
A polyester resin is one type of resins most frequently used in containers, sheets, films, fibers, and injection products, and antimony oxide or antimony triacetate is most commonly used as a catalyst during manufacturing thereof.
The antimony catalyst has advantages in that color is excellent and productivity is high due to high activity during esterification (ES) and polycondensation (P.C), but antimony is regulated as a material that is harmful to the human body due to its toxicity, and thus, there is a worldwide need to develop new catalysts that are safe to the human body and environmentally friendly. In Japan, polyester resins have been produced by using a germanium catalyst as an alternative to such limitations. However, since the price of the germanium catalyst may be ten times or more higher than that of the antimony catalyst, interests in a new catalyst that is inexpensive, harmless to the human body, and environmentally friendly have rapidly grown.
A titanium compound catalyst has been developed as an alternative to the antimony catalyst. However, there may be limitations in that a polyester resin prepared with the disclosed titanium catalyst may be not suitable for molding containers due to a yellowing phenomenon, productivity may not only be decreased due to a low reaction rate during a solid state polymerization reaction but a large amount of acetaldehyde may also be generated due to a high thermal decomposition rate in the process of forming molded products, such as containers, sheets, films, and fibers, and inherent viscosity (UV) is too low to be used as a resin for molding containers.
In order to address the foregoing limitations with respect to the titanium catalyst, a method of using titanium alkoxide, acetyl acetonate, dioxide, titanate, and phosphate, and using pyromellitic dianhydride for improving inherent viscosity during solid state polymerization is suggested as a method of manufacturing polyester by using a titanium compound catalyst in U.S. Pat. No. 6,143,837. However, information related to branching agents is limited and there may be no plan for improving color, the biggest limitation in preparing polyethylene terephthalate (hereinafter, referred to as “PET”) by using a titanium catalyst compound.
Also, in U.S. Pat. No. 5,744,571, alkyl titanate is used as a titanium catalyst compound and various color enhancers for improving colors are suggested. However, a value of b among color values may be decreased by using an organic color agent and plans for improving a solid state polymerization rate and thermal stability may not be suggested.
Further, various methods for preparing branched polyester by using polyfunctional agents are suggested in U.S. Pat. No. 4,217,440. However, the purposes of the methods, as techniques developed before titanium catalysts are produced, may not be clear and there may be no method of improving colors and no technique able to improve a reaction rate of solid state polymerization, disadvantage of the titanium catalysts.
A method of adding a blue agent and a red agent as color agents for improving color values during preparation of PET by using a titanium catalyst compound and using pyromellitic dianhydride (PMDA) as a measure capable of improving a solid state polymerization rate is disclosed in U.S. Pat. No. 7,199,210. However, since this method uses organic color agents, there may be limitations for a fundamental color enhancer, and as a plane for improving the solid state polymerization rate, only PMDA is used as a polyfunctional agent and thus, it may be lack of diversity.
Also, a method of preparing polyester for improving a yellowing phenomenon, characteristics of a titanium catalyst, by using a titanium catalyst and a magnesium compound is disclosed in U.S. Patent Publication No. 2007/0155947. However, limitations occurred during the use of the titanium catalyst, such as the reduction of a solid state polymerization rate and the generation of a large amount of acetaldehyde caused by fast thermal decomposition, may not be improved.